In general, an aspect of operation inputs with respect to a personal computer (from hereon, simply referred as “PC”) varies depending on an application program to be used (from hereon, simply referred as “application”). However, as a result of development of a graphical user interface (GUI), many applications have been designed to conduct intuitive operation inputs. Moreover, operation inputs are conducted on a desktop displayed on the display device of PCs with respect to icons of files, folders or the like. It is often the case that the operation inputs can be conducted by a common, intuitive operation even if different applications are used.
Conventionally, operation inputs for PCs have often been performed exclusively by using an input device, such as a keyboard or a mouse and clicking various icons for folders, files and the like (hereinafter, referred as “object”) displayed on a display device. However, recently, there are also many devices allowing such operation inputs for PCs to be performed highly intuitively by using a display device including a touch panel. When performing an operation input to various objects, such as various folders, files and the like, displayed on a screen by using a touch panel, instead of performing a click operation using an input device, such as a mouse and the like, generally, a (touch) operation in which the touch panel is touched with a fingertip is performed. In addition to the fingertip of the user, touch panel operations may be performed through touch operations using a pen-type device, such as a stylus.
Recently, touch panels are being loaded on mobile terminals such as cell phones, small laptop PCs and PDAs (Personal Digital Assistants), and the various functions of such mobile terminals are becoming highly diversified and sophisticated. As a result, operations similar to the operation inputs for PCs described above are also becoming available on mobile terminals that include a touch panel. In other words, by performing operation inputs by touching a touch panel loaded on a mobile terminal with their fingertip, users are able to operate folders and files displayed on the display unit of a touch panel.
In the currently dominant types of operating systems (OSs), almost all file systems have a hierarchical structure composed of directories. In other words, various data or programs can be managed as various files, and such files can be included in a single folder, and that folder can be included in another folder at a higher level. Multiple files and/or other folders can also be included in a single folder. By using the hierarchical structure of such folders, users can classify and store information very efficiently. It is also easy for users to reorganize information that has already been stored in accordance with their preferences. In particular, in basic applications of the currently dominant types of OSs, the operability and convenience for the users has been improved significantly through the use of GUIs that visualize folders and files as objects.
Generally, when operating a folder or a file in a PC, a user performs a single-click or double-click operation on an object of a folder or a file by using an input device such as a mouse. By single-clicking an object of a folder or a file, the user can select the object. In the case of a folder with a hierarchical structure, the user can perform an operation to open that folder by double-clicking the object of the folder. Through such operations for opening folders, it is possible to display other folders and/or files included in the lower hierarchy of the folder. In the case of an object of a file, the user can execute the file by double-clicking the object. Each file is associated with the applications required for executing the file, and when a specific file is executed, applications required for executing the file are launched.
In addition to the PC operations described above, when moving the location at which an object for a folder or a file is displayed on a display device, the user can place the object for a folder or a file in a hold state (selected state) by maintaining a state in which the object is clicked. In this hold state, by moving the input location of the input device such as mouse while maintaining the hold state, the user can cause the location of the object to follow the movement of the input location of the input device. By moving the location of the object to a desired location using the input device while maintaining the hold state, and then releasing the clicked state at the desired location to release the hold state, the user can determine the location of the object. Generally, the operation of moving an object while maintaining a hold state is referred to as a “drag” operation, and the operation of releasing the hold state and determining the location of the object that has been moved in the hold state is referred to as a “drop” operation. This series of operations is also referred to as a “drag-and-drop” operation.
The “single-click”, “double-click”, “drag” operation and “drop” operation described above are not performed exclusively using a input device, such as mouse, as part of PC operations, and they may also be performed using a mobile terminal that includes a touch panel. In this case, a single-click on the touch panel is performed through an operation in which the user touches the touch panel once with their fingertip, and a double-click is performed through an operation in which the user quickly touches the touch panel twice consecutively with their fingertip. To perform a drag operation on the touch panel, the user keeps an object displayed on the touch panel in a hold state in which the object is touched (pressed) by their fingertip, and moves (tracing) their fingertip while pressing the touch panel. To perform a drop operation on the touch panel, after moving the object through a drag operation, the user releases the fingertip from the touch panel to release the hold state.
Through operations such as those described above, even when operating a terminal that includes a touch panel, the user is able to perform operation inputs similar to PC operations performed with an input device such as mouse. Because such easy and intuitive operation inputs can be performed, the use of terminals, such as mobile terminals, that include a touch panel has been increasing in recent years.
Touch panels included in conventional mobile terminals have generally included only functions for performing location detection to determine the location being touched by the fingertip of the user. However, recently, there have been proposals for touch panels that detect not only the location being touched on the touch panel, but also the pressing force to touch the touch panel (see Patent Document 1, for example).
This input device described in the Patent Document 1 measures the pressing force used on a touch panel when an object on the display unit of the touch panel is touched and specified by a user, and if the pressing force exceeds a prescribed value, a prescribed process is performed. In other words, this input device measures the pressing force of a pressing input performed by a user in relation to a keyboard screen displayed on a display unit, and if the pressing force is equal to or below a prescribed value, the display information of a prescribed range including the key specified on the keyboard screen is obtained and can be displayed at a display region at a location different from the keyboard screen. If the pressing force of the pressing input exceeds a prescribed value, this input device obtains information on the key corresponding to the location of the pressing input and can perform the input process of the key or a process to execute a program associated with the key.